Enum snafu::guide::examples::basic::Error

[−] Show declaration

pub enum Error {
    Leaf {
        user_id: i32,
    },
    Intermediate {
        source: Error,
    },
}

[−] Expand description

An enumeration of possible errors.

This will create a number of context selectors:

• Leaf
• Intermediate

Leaf errors

Context selectors for error variants without a source, such as Leaf, have methods to construct them, such as Leaf::build or Leaf::fail. The ensure macro also accepts these kinds of context selectors.

use snafu::ensure;

fn always_fails() -> Result<(), Error> {
    Leaf { user_id: 42 }.fail()
}

fn sometimes_fails(user_id: i32) -> Result<(), Error> {
    ensure!(user_id > 0, Leaf { user_id });
    Ok(())
}

Intermediate errors

Context selectors for error variants with a source, such as Intermediate, are intended to be used with the ResultExt::context family of methods.

use snafu::ResultExt;

fn load_config_file() -> Result<usize, Error> {
    let config = std::fs::read_to_string("/path/to/my/config/file").context(Intermediate)?;
    Ok(config.len())
}

Variants

Leaf

[−] Show fields

Fields of Leaf

user_id: i32

Intermediate

[−] Show fields

Fields of Intermediate

source: Error

Trait Implementations

impl Debug for Error[+]

[+] Show hidden undocumented items

fn fmt(&self, f: &mut Formatter<'_>) -> Result[−]

Formats the value using the given formatter.

impl Display for Error[+]

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fn fmt(&self, __snafu_display_formatter: &mut Formatter<'_>) -> Result[−]

Formats the value using the given formatter.

impl Error for Error where
    Self: Debug + Display, [+]

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fn description(&self) -> &str[−]

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>[−]

The lower-level source of this error, if any.

pub fn backtrace(&self) -> Option<&Backtrace>[−]

🔬 This is a nightly-only experimental API. (backtrace)

Returns a stack backtrace, if available, of where this error occurred.

impl ErrorCompat for Error[+]

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fn backtrace(&self) -> Option<&Backtrace>[−]

Returns a Backtrace that may be printed.

impl<__T0> IntoError<Error> for Leaf<__T0> where
    Error: Error + ErrorCompat,
    __T0: Into<i32>, [+]

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type Source = NoneError

The underlying error

fn into_error(self, error: Self::Source) -> Error[−]

Combine the information to produce the error

impl IntoError<Error> for Intermediate where
    Error: Error + ErrorCompat, [+]

[+] Show hidden undocumented items

type Source = Error

The underlying error

fn into_error(self, error: Self::Source) -> Error[−]

Combine the information to produce the error